Conventionally, as a run-flat tire that can travel during a punctured condition, a side reinforced type run-flat tire has been proposed (see, for example, Japanese Unexamined Patent Application Publication Nos. H07-304312A and 2008-296873A) that has a side reinforcing layer having a falcated cross-sectional shape disposed on the inner side of the side wall portion.
With this type of side reinforced type run-flat tire, it is common that the thickness of the side reinforcing layer is made greater and a rubber composition having high hardness is used in the side reinforcing layer in order to increase durability during run-flat traveling.
However, when increasing the thickness of the side reinforcing layer and increasing hardness of the rubber composition that composes the side reinforcing layer, there is a problem in that ride comfort degrades during regular traveling in conjunction with the increase in rigidity of the side wall portion. Therefore, a way is sought to enhance durability during run-flat traveling without degrading ride comfort. Furthermore, if a spring constant of the tire is reduced in order to secure ride comfort, there is also a problem in that steering stability degrades during regular traveling.